This invention relates to a magnetic head formed of metallic magnetic material adapted to be brought into contact with a magnetic recording medium to record and reproduce signals on and from the recording medium, and a method of producing same.
In a contact type magnetic head, what is most important in achieving improved performance in practical use is to minimize wear caused on the head core by the sliding contact with the recording medium, particularly wear caused on the head gap portion that performs the operation of recording and reproducing the signals. Wear caused on the head core, particularly the head gap portion, causes changes to occur in the properties of the magnetic head due to its deformation caused by the wear, thereby usually causing marked deterioration in performance.
In recent years, there has been a tendency to use, in producing magnetic recording mediums, magnetic material of high coercive force (Hc) for the purpose of improving the recording density. For example, what is generally referred to as a metal tape having a coat of Fe or Fe-Co alloy powder applied to the base has a very high coercive force or Hc=1000-2000 Oe. Magnetic heads used for recording and reproducing the signals on and from such recording medium include a head having a head core formed of ferrite having high wear resistance. However, owing to the fact that the saturation magnetic flux density of ferrite Bs=4.pi.Is (where Is is the value of saturation magnetization) is not high enough, ferrite has had the disadvantage that the head core undergoes magnetic saturation and causes distortion of the recorded signals or makes it impossible to give sufficiently high residual magnetization to the medium to make satisfactory recordings. More recently, the attention of the electronic industries has been attracted to magnetic metal material of high saturation magnetic flux density, such as Fe-Si-Al alloys or amorphous alloys obtained by super-rapid quenching of molten 3d transition metal alloys containing substantially 20% of vitrifying elements such as P, C, B, Zr, etc., because of their high hardness. In magnetic heads including head cores formed of such metallic magnetic material, the head cores generally used are formed as follows. When the thickness d of the head core is sufficiently greater than the depth of the surface layer of the core material ds=5040.sqroot..rho..mu.f (cm) where f is the frequency (Hz) of the signal to be recorded, .mu. is the permeability of the head core materia and .rho.(.OMEGA.-cm) is the electrical resistivity, or when d&gt;&gt;2 ds, thin sheets of magnetic metal each of which having thickness substantially equal to 2 ds and having been worked to have a predetermined core shape are stacked and bonded together by resinous adhesives to fabricate a core of the predetermined thickness d. Sendust is a material which is difficult to be processed to such thin sheet. On the other hand, amorphous alloys obtained by super-rapid quenching can readily be formed into a strip of about 50 .mu.m in thickness, so that many studies on using them as head core material suitable for recording medium of high coercive force (Hc) have been carried out. However, amorphous alloys obtained by super-rapid quenching are not without disadvantages. One of such disadvantages is that, in spite of the fact that such amorphous alloy has Vickers hardness Hv=500-1000 which is extremely high as a metallic material, when it is used as a magnetic head it shows wear of the same degree as or sometimes higher than that of sendust which has Vickers hardness Hv=500.